Besides the ABCs(of which I quit buying at about volume 4-5, been doing this since late '70s) Get a Lyman manual first, then buy others. I have at least a couple dozen manuals, but it is not like I bought them all at once. A mistake I have seen many times is people sometimes want to load really hot, well you have to be careful, work up a load, and if you get a good warm load and change anything, reduce and start over. Wear safety glasses, I have seen 3 blown up lee auto primes, two brought in when I worked at a gun shop, and one blew up on a good friend of mine, happened in his living room, his wife bout killed him, he was wearing glasses. The gun should be fine stock, unless you want to shoot cast bullets out of it, I shoot plated out of my 20, and I am a caster.
Glock makes a 6 inch IIRC hunting barrel, as a lot of states require hunting handguns to have a 5 inch barrel. A buddy of mine has killed deer with his. Oh, buy some mags, I have had my 20 a while and at the height of the clinton foolishness used mags were close to 100$
My favorite powders , not in order are AA#9, Power Pistol, Blue Dot, stuff like that. I have a surplus of Longshot I need to work up a load for, it has given me problems, worked up a tack driving load that had enough juice to hit at 50 yards out of my G-35, but the same load in an HK USP Compact 40 nearly keyholes, and the load I worked up for the HK, AA#7 I think, is more accurate than the longer Glock, and shoots just as bad out of the Glock as the Glock ammo shoots out of the HK, I hate that, have grabbed the wrong ammo on the way to where I shoot- it pays to experiment. BTW, I taught myself to reload, with the help of manuals and magazines, of which Handloader is by far the best, most gun rags I hate myself for buying, They have gone down hill bad in the last 30 years. Congrats on the 20, my favorite Glock I own, and take it slow and careful reloading and you will be fine.
NRA Certified Instructor